JPH03284942A - Alloyed galvanized steel sheet coated with organic resin - Google Patents

Abstract

PURPOSE:To impart high powdering resistance and high flaking resistance and obtain an alloyed hot-dip zinc-coated steel sheet coated with an organic resin, which has highly sliding characteristics, by forming an organic resin layer containing a specific weight percent of fluorocarbon resin particles on the surface of the iron sheet in a specific amount of coating. CONSTITUTION:In an alloyed hot-dip zinc-coated steel sheet coated with an organic resin, an organic resin layer forming an organic resin coating contains 2-40wt.% of fluorocarbon resin particles. If the content of the fluorocarbon resin particles is less than 2wt.%, the friction coefficient of the coating becomes greater and, if the content thereof exceeds 40wt.%, the organic resin layer tends to be peeled off the alloyed hot-dip zinc-coated steel sheet. An amount of the organic resin coating applied to the iron sheet is within a range of 0.1-5g/m<2> and, if an amount of application is smaller than 0.1g/m<2>, the effects of lubricating properties and resistance to corrosion are not sufficient. On the other hand, if it exceeds 5g/m<2>, the organic resin coating tends to be peeled off during a pressing operation and is attached to a metallic mold, whereby there is the possibility of causing defect in the pressing. Accordingly, by adjusting one or both of the content of particles and the amount of the coating to be applied to the steel sheet, the friction coefficient of the iron sheet can be optimized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an organic resin-coated alloyed hot-dip galvanized steel sheet having excellent corrosion resistance and suitable for use in automobiles, home appliances, building materials, etc.

BACKGROUND ART Strain-strain alloyed hot-dip galvanized steel sheets have conventionally been widely used for rust prevention of automobile garage bodies. In recent years, in order to strengthen the rust prevention ability, the amount of plating has been increased from the conventional 45g/rd to 6.
There is a growing tendency for it to increase to about 0 g/rrr or more.

However, conventionally, when alloyed hot-dip galvanized steel sheets are used, for example, in automobile bodies, there is a problem that powdering or flaking occurs during press working. That is, when pressing an alloyed hot-dip galvanized steel sheet, the steel sheet deforms, or when the plating layer slides against the mold, the plating layer peels off into fine powder (powdering). Or, it peels off into flakes.

This phenomenon becomes more noticeable as the coating weight on alloyed hot-dip galvanized steel sheets increases.As mentioned above, in recent years, when the coating weight has been increasing, prevention of this phenomenon has become more important (as requested). Especially,
Flaking occurs on sliding parts such as drawbeads where the surface pressure is extremely high when the coating weight is 50 g/rtT or more.

The peeled off pieces caused by this flaking are large in size, so
When it adheres to the press mold, it causes press defects called bulges and bumps, which necessitates frequent cleaning of the mold and significantly reduces productivity.

Generally, the alloyed hot-dip galvanized layer consists of an r phase (28 to 21% iron) and a δ phase (11° iron 4 to 7.0%) in order from the iron substrate side.
), ζ phase (7.2 to 6.0% iron), and η phase (zinc with a small amount of solid solution of iron), which are composed of iron-zinc alloy phases, and the temperature and time of alloying treatment are increased. By increasing the diffusion of iron into the plating layer (hereinafter referred to as "increasing the degree of alloying"), the thickness of the alloy phase with a high iron content increases.

Since the plating layer peels off due to powdering and flaking, it is the hard and brittle r-phase, so in order to prevent such peeling of the plating layer, the degree of alloying is reduced and the thickness of the r-phase is reduced. That's fine.

However, when the degree of alloying is reduced, the average iron content decreases and ζ and η phases with low iron content tend to remain near the surface layer. Therefore, the sliding resistance during press forming increases, making it difficult for the alloyed hot-dip galvanized steel sheet to flow into the press mold, making it easier for the press product to break. This phenomenon is particularly noticeable in thickly plated steel sheets with a large coating weight and a coating weight of 50 g/i or more, where iron is difficult to diffuse to the surface.

As explained above, both the problems of powdering and flaking and the problems of sliding can be solved by adjusting the degree of alloying of the galvannealed steel sheet.
This is difficult for thick steel plates of g/rrI or more.

Therefore, conventionally, in order to solve the above problem, for example,
First, 2 to 5 g of hard iron-based electroplating is applied to the surface layer.
Second, use a highly workable rust preventive oil that has improved press formability by adding oil-based agents, extreme pressure agents, etc.; Third, use wax, metal soap, Dry lubricant coatings such as molybdenum sulfide have been used.

However, according to the first method, since the iron-based electroplated layer has strong tensile stress, the alloyed hot-dip galvanized layer is restrained and difficult to follow the deformation of the steel base, resulting in still powdering. is likely to occur. Moreover, in this method, electroplating equipment is installed on the outlet side of the hot-dip galvanizing line that produces alloyed hot-dip galvanized steel sheets, or the alloyed hot-dip galvanized steel sheet coils produced in the hot-dip galvanizing line are further coated. It is necessary to transfer the product to another electroplating line and apply iron-based electroplating, which increases manufacturing costs.

According to the second method, the above-mentioned highly processable rust preventive oil with improved press formability usually has a high viscosity and is difficult to handle, as well as difficult to degrease after processing. . Furthermore, since dust tends to adhere to the surface, when cleaning oil is used before pressing to remove it, most of the rust-preventing oil is also removed at the same time, resulting in the problem of deterioration of press formability. occurs.

In the method using the third dry lubricating film, in order to improve paint film adhesion when painting after pressing, it is necessary to remove the film by degreasing;
The above-mentioned dry lubricating film cannot be removed under the same conditions as ordinary anti-rust oils, so if the degreasing properties are improved, a problem arises in that the film is removed during cleaning before pressing. Furthermore, depending on the type of dry lubricant coating, the peeled coating may be deposited on the mold, making it necessary to clean the mold. In addition, the dry lubricating film does not have corrosion resistance, and there is a risk that rust will occur on the iron during temporary storage before and after pressing. The present invention has been made to solve the above-mentioned problems, and the present invention has been made to solve the above-mentioned problems. An object of the present invention is to provide an organic resin-coated alloyed hot-dip galvanized mesh sheet that imparts high powdering resistance and flaking resistance and has high sliding properties in hot-dip galvanized steel sheets.

In the organic resin-coated alloyed hot-dip galvanized steel sheet according to the present invention, the organic resin layer containing 2 to 40% by weight of fluororesin particles coats the steel sheet at a coating amount of 0.1 to 5 g/rrf. It is characterized by being formed on the surface.

In the organic resin-coated alloyed hot-dip galvanized bait according to the present invention, the organic resin layer forming the organic resin coating contains 2 to 40% by weight of fluororesin particles. When the amount of fluororesin particles is less than 2% by weight, the coefficient of friction of the resulting coating is large and the sliding properties are not improved. However, when it exceeds 40% by weight, the organic resin layer tends to peel off from the alloyed hot-dip galvanized steel sheet during press processing because the fluororesin generally has a weak bonding force with the resin, and the adhesion of the coating film also deteriorates. do. In particular, in the present invention, the amount of fluororesin particles in the organic resin coating is preferably 5 to 35% by weight.

In order to obtain the maximum effect of such fluororesin particles, the particle size of the fluororesin is preferably in the range of 0.01 to 2 μm. When the particle size exceeds 2 μm,
When preparing an organic resin coating composition for forming a resin layer, it is difficult to uniformly disperse fluororesin particles in the resin emulsion. The adhesion and the adhesion of the obtained organic resin film to the coating film decrease. On the other hand, when the particle size of the fluororesin is smaller than 0.01 μm, the effect of improving slidability by adding the fluororesin decreases.

Examples of the above-mentioned fluororesin include tetrafluoroethylene resin (PTFE), trifluorochloroethylene resin, vinylidene fluoride resin, vinyl fluoride resin, ethylene/tetrafluoroethylene copolymer resin, and tetrafluoroethylene resin.・Hexafluorinated propylene copolymer resin etc. can be mentioned. These fluororesins are commercially available as emulsions.

In the present invention, the organic resin coating is made of silica particles.
It is preferable to contain 1 to 30% by weight as O□. According to the present invention, even if the organic resin film does not contain silica,
A coating having lubricity and degreasing properties can be obtained, and by incorporating silica particles, the lubricity and corrosion resistance of the coating can be further improved.

From this point of view, the amount of silica particles in the organic resin coating is
It is preferable that Sing is 1% by weight or more. On the other hand, when the amount exceeds 30% by weight, silica acts as a lubricant, increasing the coefficient of friction of the coating and reducing the lubricity. In particular, in the present invention, the organic resin coating preferably contains silica particles in a range of 5 to 15% by weight.

In order to maximize the effects of silica as described above, the particle size of silica is preferably in the range of 1 to 20 mμ. -For boat fishing, the smaller the particle size of silica, the denser and more adhesive the organic resin coating will be, and the better its corrosion resistance, coating adhesion, lubricity, etc. However, even if extremely small particles are used, the above-mentioned effects will still be achieved, especially if extremely small particles are used.
Therefore, in the present invention, the silica only needs to have a particle size of 1 ma or more. On the other hand, 20 mμ
If it exceeds this, the corrosion resistance and lubricity of the coating will be reduced.

In particular, in the present invention, the silica used has a particle size of 3 to 3.
A range of Ionμ is preferred.

Such silica is generally known as colloidal silica, and is commercially available as, for example, Snowtex-XS or 55 (manufactured by Nissan Chemical Industries, Ltd.).

In the present invention, the base resin constituting the organic resin coating may be one that does not cause aggregation when mixed with the fluororesin emulsion or colloidal silica.
Any resin can be used without limitation, but epoxy-based Polyolefin resins such as polyethylene, polypropylene, urethane resins, and acrylic resins are preferably used.

In the present invention, the amount of organic resin coating attached to the steel plate is
It is necessary that it is in the range of 0.1 to 5 g/m. When the amount of the organic resin coating on the steel plate is less than O,I g/rri, the effect of improving lubricity and corrosion resistance is insufficient, whereas when it exceeds 5 g/%, the organic resin coating is difficult to press. It tends to peel off during processing and may adhere to the mold, causing press defects. The smaller the friction coefficient of the steel plate subjected to press forming, the better. The smaller the coefficient of friction, the easier it is for the steel plate to flow into the press die, which is advantageous in preventing the steel plate from breaking, but on the other hand, the tension acting on the flange itself becomes weaker, causing wrinkles to occur. This is because the tension acting within the mold becomes weaker, and defects such as spring back and surface distortion are more likely to occur.

Therefore, the friction coefficient of the steel plate needs to be adjusted to an optimal value. The coefficient of friction of a steel plate is determined by the amount of fluororesin particles in the coating, that is, the content (% by weight) of fluororesin particles in the coating.
Since it decreases in proportion to the product of and the amount of film adhered to the steel plate (g / rrr), by adjusting either or both of the content of the fluororesin particles and the amount of film adhered to the steel plate. , the friction coefficient of the steel plate can be optimally designed.

When it is desired to increase the amount of film deposited from the viewpoint of corrosion resistance or paintability, the coefficient of friction of the steel plate must be maintained at a constant level by correspondingly reducing the content of fluororesin particles in the film. I can do it.

In the present invention, the alloyed hot-dip galvanized mesh plate particularly includes:
Although not limited to this, according to the present invention, flaking resistance, gluing resistance, and
Although it can improve lubricity, paintability, corrosion resistance, etc., the organic resin coating according to the present invention is particularly useful for thick alloyed hot-dip galvanized steel sheets with a coating weight of 50 g/rrf or more, which tends to deteriorate flaking resistance. When applied, flaking is effectively prevented. Further, in the present invention, the organic resin coating may be applied only to one side of the alloyed hot-dip galvanizing,
It may also be applied to both sides.

The organic resin-coated steel sheet according to the present invention can be formed directly by applying the coating composition on the alloyed hot-dip galvanizing in a continuous alloying hot-dip galvanizing line or off-line and drying. However, during processing,
Alternatively, when it is necessary to improve the adhesion between the alloyed hot-dip galvanized layer and the organic resin coating after applying the paint, or to improve the corrosion resistance before and after processing, the method according to the present invention may be applied after applying chromate treatment to the alloyed hot-dip galvanized steel sheet. It is advantageous to form an organic resin coating. Here, the chromate treatment is not limited at all, and coating type chromate treatment or reactive chromate treatment may be performed depending on the specifications of the production line.

The resin-coated alloyed hot-dip galvanized steel sheet according to the present invention has excellent lubricity even without applying oil such as rust preventive oil or press oil. No problems such as dissolution or deterioration of lubricity occur.

As described above, according to the organic resin-coated alloyed hot-dip galvanized steel sheet of the present invention, the organic resin coating acts as a kind of dry lubricating coating during press molding, and this coating alone or Through the combined action of anti-corrosion oil and cleaning oil, it reduces the friction coefficient of the steel plate and improves the sliding properties between the alloyed hot-dip galvanized steel plate and the mold, thus effectively preventing the steel plate from breaking. be able to.

Furthermore, in order to reduce the friction coefficient of the steel plate, the shear stress applied to the brittle phase that exists between the coating layer and the base steel plate when the alloyed hot-dip galvanized steel plate and the mold slide is reduced, and the powder Prevents ringing and flaking.

Moreover, the organic resin coating layer according to the present invention is not removed by rust preventive oil or cleaning oil, nor is it dissolved or removed even by degreasing before painting, and remains as it is on the surface layer of the alloyed hot-dip galvanizing. As a corrosion-resistant coating, it contributes to the rust prevention of steel sheets in conjunction with the alloyed hot-dip galvanized plating phase, and is also suitable as a base coating for painting, and has excellent coating adhesion. Furthermore, since there is no need to apply high viscosity anti-rust oil, workability is also excellent.

Implementation (2) The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Plate thickness 0.811II11, adhesion 62g/rrf, average F
Coating-type chromate (Cosmer C manufactured by Kansai Paint ■) was applied to an alloyed hot-dip galvanized steel sheet with an e content of 9.8% at a Cr coverage of 60■/m2, and after drying, the composition shown in Table 1 was applied. An organic resin coating layer was formed.

Regarding the resin-coated alloyed hot-dip galvanized steel sheet obtained in this way, the friction coefficient, cylindrical deep drawing, flaking resistance,
Paint adhesion and corrosion resistance were examined using the methods described below.

The results are shown in Table 1.

The test material steel plate coated with anti-corrosion oil was sandwiched between 20 mm x 20 sim molds with a surface pressure of 3 kgf/arm.
Pull at a speed of 00m+/min to apply pressure to the steel plate of N,
When the tensile force applied to the steel plate is F, the friction coefficient μ=F/
Obtained from 2N.

■For the sample steel plate coated with anti-corrosion oil, the punch diameter was 50 m.
The critical drawing ratio was determined with a wrinkle holding force of 600 kgf/+m''.The larger the limiting drawing ratio, the better the lubricity.
The steel plate is less likely to break during press forming.

il''=Raw hole outside method As shown in Fig. 1, the test material steel plate coated with anti-corrosion oil was set to have a clearance of 0.6 m between the dies, a machining speed of 19.2 m, and an ironing rate of 25%. After this process,
The outer sliding part of the sample material was taped, and the amount of adhered foil pieces was visually evaluated, and evaluated in four grades: ◎, O1Δ, and × in descending order of flaking resistance.

Satotenno 1 test material was subjected to dipping phosphate treatment and cationic electrodeposition coating (20
μm), then the 1st cabinet foundation test was conducted. ◎ indicates that the coating film did not peel off, ○ indicates that the area around the cutter scratch partially peeled off, △ indicates that 1 to 10 of the 100 base marks peeled off, × indicates that 11 or more of the 100 base marks peeled off. indicates that it has peeled off.

(2) Requirements After Erichsen overhang processing (overhang height 60) was performed on the sample material, a salt spray test (120 hours) was conducted and the white rust incidence rate was evaluated.

From Examples 1 to 3 and Comparative Examples 1 and 2, as the content of fluororesin particles increases, the friction coefficient decreases, the critical drawing ratio increases, the lubricity improves, and the flaking resistance increases. However, when the content reaches 50%, the film adhesion deteriorates.

From Examples 2.4 and 5 and Comparative Example 3, as the content of silica particles increases, the corrosion resistance improves, but when the content of silica particles reaches 40%, the coefficient of friction increases and the lubricity decreases. It is shown that it deteriorates.

From Examples 5 to 7 and Comparative Example 4, it was found that when the amount of organic resin coating was 0.05 g/nf, there was no effect of lowering the friction coefficient;
It is shown that at 0.2 g/rrI or more, the coefficient of friction decreases in proportion to the increase in the amount of coated film.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an apparatus system used in Examples to examine flaking resistance of alloyed hot-dip galvanized mesh plates.

Claims (7)

[Claims] (1) Organic resin-coated alloying characterized in that an organic resin layer containing 2 to 40% by weight of fluororesin particles is formed on the surface of a steel plate at a coating amount of 0.1 to 5 g/m^2 Hot-dip galvanized steel sheet. (2) The organic resin-coated alloyed hot-dip galvanized steel sheet according to claim 1, wherein the organic resin layer further contains 1 to 30% by weight of silica particles as SiO_2. (3) The organic resin-coated alloyed hot-dip galvanized steel sheet according to any one of claims 1 to 2, wherein the fluororesin particles have a particle diameter of 0.01 to 2 μm. (4) The organic resin-coated alloyed hot-dip galvanized steel sheet according to any one of claims 2 to 3, wherein the silica particles have a particle diameter of 1 to 20 mμ. (5) Adhesion amount of alloyed hot-dip galvanized layer is 50g/m^
The organic resin-coated alloyed hot-dip galvanized steel sheet according to any one of claims 1 to 4, characterized in that the number of galvanized steel sheets is 2 or more. (6) The organic resin-coated alloyed hot-dip galvanized steel sheet according to any one of claims 1 to 5, wherein an organic resin layer is formed on the chromate treatment layer. (7) Organic resin-coated alloying according to any one of claims 1 to 6, wherein the base resin constituting the organic resin layer is epoxy, polyolefin, urethane, or acrylic. Hot-dip galvanized steel sheet.